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Biomedical subjects

G Simon

Publications and source records attributed to G Simon.

At least 19 recordsLinked to original sources
PubMed2006

Hyper-Raman scattering from vitreous boron oxide: coherent enhancement of the boson peak.

Hyper-Raman scattering spectra of vitreous B(2)O(3) are compared to Raman scattering ones. Particular attention is given to the low-frequency boson peak which relates to out-of-plane rigid librations of planar structural units, mostly boroxols. While the Raman strength can be accounted for by the motions of single units, the hyper-Raman signal exhibits a unequaled enhancement due to coherent librations of several boroxols. This important distinction is explained by the different symmetry properties of the polarizability and hyperpolarizability tensors of the structural units.

Journal Article↗
PubMed2006

Clinical depression and risk of out-of-hospital cardiac arrest.

BACKGROUND: The association of depression with coronary heart disease-related mortality has been widely recognized. This finding may partly reflect an association between depression and sudden death, in part because the imbalance between sympathetic and parasympathetic tone is altered in depressed subjects. We, thus, investigated whether the presence and severity of clinical depression was associated with a higher risk of sudden cardiac death. METHODS: We used data from a population-based case-control study of risk factors for incident out-of-hospital cardiac arrest (CA) conducted among enrollees of a health maintenance organization in western Washington State. Cases (n = 2228) were aged 40 to 79 years and experienced CA between January 1, 1980, and December 31, 1994. Controls (n = 4164) were a stratified random sample of enrollees defined by calendar year, age, sex, and prior heart disease. Clinical depression was defined as physician diagnosis of depression or use of antidepressant treatment within the year before the event. Referral to mental health clinics or hospitalization for depression defined severe depression. RESULTS: Clinically depressed patients had a higher odds ratio (OR) of CA (1.88; 95% confidence interval [CI], 1.59-2.23), which persisted after adjustment for confounders (OR, 1.43; 95% CI, 1.18-1.73). The association was observed in both sexes, in various age groups, and in subjects with prior physician-diagnosed heart disease (OR, 1.27; 95% CI, 1.01-1.60) and without prior physician-diagnosed heart disease (OR, 1.71; 95% CI, 1.22-2.41) (P = .13 for the interaction). Compared with nondepressed subjects, the risk of CA was increased in less severely depressed subjects (OR, 1.30; 95% CI, 1.04-1.63) and further increased in severely depressed subjects (OR, 1.77; 95% CI, 1.28-2.45) (P<.001 for trend). CONCLUSION: Clinical depression may be associated with a higher risk of CA independently of established coronary heart disease risk factors.

Adult↗
PubMed2006

[MRI of arthritis with the USPIO SH U 555 C: optimization of T1 enhancement].

PURPOSE: To optimize contrast agent dose and pulse sequence parameters in order to achieve a maximal T1 enhancement in arthritic knee joints with ultra small superparamagnetic iron oxides (USPIO)-enhanced MRI. MATERIALS AND METHODS: Antigen-mediated arthritis was induced in the right knee of nine Sprague Dawley rats. The arthritic knee joint as well as the contralateral normal knee were investigated in a 2 Tesla MR scanner before as well as in short intervals up to 2 h after USPIO injection, using T1-weighted gradient echo (GE) sequences. Three rats each received intravenous injections of the new USPIO SHU 555 C (SH U 555 C, Schering AG, Berlin) at doses of 40, 100 and 200 micromol Fe/kg. Pulse sequence parameters of the GE-sequence were optimized by varying flip angles (alpha) and echo times (TE). Changes in signal intensities (SI) of the arthritic knee and contralateral normal knee were quantified as DeltaSI (%) = /([SIpost - SIpre] / SIpre) x 100 %/ and compared with histopathology. RESULTS: Histology of the arthritic knees demonstrated a marked inflammatory proliferation of the synovium. The USPIO SH U 555 C caused a significant increase in signal intensity of the arthritic joints on T1-weighted MR images (p < 0.05). This effect was optimized using a flip angle of 60-70 degrees, a minimal TE and a dose of 200 micromol Fe/kg. Visually the contralateral normal knee did not show any USPIO enhancement. CONCLUSION: Inflammation can be depicted with marked T1 enhancement by the USPIO SH U 555 C using high contrast agent doses and optimized MR pulse sequence parameters.

Animals↗
PubMed2005

Detection of hepatocellular carcinoma: comparison of Gd-DTPA- and ferumoxides-enhanced MR imaging.

The aim was to compare the diagnostic performance of dynamic Gd-DTPA- and ferumoxides-enhanced MRI for hepatocellular carcinoma (HCC). Twenty-five patients with chronic hepatitis or liver cirrhosis underwent both dynamic gadopentetate- and ferumoxides-enhanced MRI studies of the liver for HCC detection on the same day. MR data of both studies were retrospectively and independently analyzed. Two observers determined in consensus the grade of diffuse fibrotic liver changes (mild, moderate or severe) and the number of focal lesions. HCCs were confirmed by histology (n=22) and/or follow-up studies for at least six months (n=64). Differences in results obtained from both MR data sets were tested for significance with the McNemar's test (p<0.05). Ferumoxides-enhanced MR images detected 84 of 99 hepatic lesions, including 82 of 86 HCCs and 2 false positive, nonmalignant lesions, while Gd-DTPA-enhanced MR images detected 92 of 99 hepatic lesions, including 81 of 86 HCCs and 11 false positive, nonmalignant lesions. Sensitivity of MRI for detection of HCCs was not significantly different between ferumoxides-enhanced (95.3%; p>0.05) and Gd-DTPA-enhanced scans (94.2%). Gd-DTPA- and ferumoxides-enhanced MRI perform equally well for HCC detection. The majority of small hypervascular hepatic lesions, detected on dynamic Gd-DTPA-enhanced MRI but not on ferumoxides-enhanced MRI, represent no HCCs.

Adult↗
PubMed2004

Postexercise increase of free fatty acids. A qualitative indicator for free fatty acid utilisation during exercise?

AIM: The purpose of this study was to verify the hypothesis that the postexercise increase (PEI) of plasma free fatty acid (FFA) concentrations after cessation of exercise is a suitable qualitative indicator for the FFA utilisation during the foregoing exercise. METHODS: Fourteen, 17 and 23 healthy subjects participated in 3 test series performing several prolonged exercise protocols (PEP) on a bicycle ergometer. During and after cessation of the PEP heart frequency, lactate and FFA were measured. RESULTS: Fasting resulted in an increase of PEI (90%, p<0.05) and the synergistic use of upper body muscles during cycling caused a significant rise of PEI compared to "regular" cycling (39%, p<0.01). Increasing workload step by step produced continuously rising PEI (p<0.05), only from 42% to 50% of maximal workload PEI decreased by 17% (p=n.s.). CONCLUSION: The results support the hypothesis that PEI is a suitable qualitative indicator for FFA utilisation during a foregoing exercise. Furthermore the results indicate that there is a maximum of FFA utilisation in the legs at 40% of maximum workload during cycling and that the upper body muscles contribute substantially to total body FFA turnover at high inten-sities, an aspect to which possibly too little attention has been paid to when quantifying FFA turnover during cycling.

Adult↗
PubMed2003

Parametric dependence of single-bubble sonoluminescence spectra.

We present experimental spectra of single sonoluminescing bubble in water at different dissolved argon concentrations and excitation levels. All the relevant experimental conditions are either measured directly or derived from measured quantities for each spectrum, thus the parametric dependence of the spectra can be analyzed. To characterize the data in a given wavelength interval we fitted the shape of the spectra with the Planck function. The effective temperatures obtained from these fits lie in the range 12,000-18,000 K, practically independent of the expansion ratio, while the intensity normalized by the volume of the bubble increases with the expansion ratio as a power law. The effective temperatures decrease with the pressure amplitude for each argon concentration, while the light intensity, measured with a photomultiplier tube, increases. These observations suggest that the increased energy input due to the higher pressure amplitudes results in an increased number of less energetic photons as compared to the case of a lower excitation level.

Journal Article↗
PubMed2003

Alternative method to deduce bubble dynamics in single-bubble sonoluminescence experiments.

In this paper we present an experimental approach that allows to deduce the important dynamical parameters of single sonoluminescing bubbles (pressure amplitude, ambient radius, radius-time curve). The technique is based on a few previously confirmed theoretical assumptions and requires the knowledge of quantities such as the amplitude of the electric excitation and the phase of the flashes in the acoustic period. These quantities are easily measurable by a digital oscilloscope, avoiding the cost of the expensive lasers or ultrafast cameras of previous methods. We show the technique in a particular example and compare the results with conventional Mie scattering. We find that within the experimental uncertainties these two techniques provide similar results.

Journal Article↗
PubMed2003

Cytotoxic pentacyclic triterpenes from Combretum nigricans.

A new pentacyclic triterpene, 11alpha-acetoxy-20,24-epoxy-25-hydroxy-dammar-3-one (1), has been isolated from the African tree Combretum nigricans, together with the known corresponding diol, 20,24-epoxy-11alpha, 25-dihydroxy-dammar-3-one (2). They are responsible, at least in part, for the cytotoxic activity of the methanolic extract of the plant.

Antineoplastic Agents↗
PubMed2003

Behavioural factors associated with symptom outcomes in a primary care-based depression prevention intervention trial.

BACKGROUND: A randomized trial of a primary care-based intervention to prevent depression relapse resulted in improved adherence to long-term antidepressant medication and depression outcomes. We evaluated the effects of this intervention on behavioural processes and identified process predictors of improved depressive symptoms. METHOD: Patients at high risk for depression recurrence or relapse following successful acute phase treatment (N=386) were randomly assigned to receive a low intensity 12-month intervention or continued usual care. The intervention combined education about depression, shared decision-making regarding use of maintenance pharmacotherapy and cognitive-behavioural strategies to promote self-management. Baseline, 3, 6, 9 and 12-month interviews assessed patients' self-care practices, self-efficacy for managing depression and depressive symptoms. RESULTS: Intervention patients had significantly greater self-efficacy for managing depression (P<0.01) and were more likely to keep track of depressive symptoms (P<0.0001), monitor early warning signs (P<0.0001), and plan for coping with high risk situations (P<0.0001) at all time points compared to usual care control patients. Self-efficacy for managing depression (P<0.0001), keeping track of depressive symptoms (P=0.05), monitoring for early warning signs (P=0.01), engaging in pleasant activities (P<0.0001) and engaging in social activities (P<0.0001) positively predicted improvements in depression symptom scores. CONCLUSIONS: A brief intervention designed to target cognitive-behavioural factors and promote adherence to pharmacotherapy in order to prevent depression relapse was highly successful in changing several behaviours related to controlling depression. Improvements in self-efficacy and several self-management behaviours that were targets of the intervention were significantly related to improvements in depression outcome.

Antidepressive Agents↗
PubMed2002

Budesonide/formoterol in a single inhaler versus inhaled corticosteroids alone in the treatment of asthma.

The aim of this study was to evaluate the efficacy (expressed as effect on lung function) and tolerability of Symbicort (budesonide/formoterol in a single inhaler) in children with asthma. This was a double-blind, double-dummy, randomized, parallel-group, multicenter trial. After a 2-4-week run-in period, 286 asthmatic children (177 boys, 109 girls; mean age, 11 years; mean forced expiratory volume in 1 sec (FEV(1)), 75% predicted normal), previously treated with inhaled corticosteroids (average dose 548 microg/day), were randomized to 12 weeks' treatment with either budesonide/formoterol 80/4.5 microg, two inhalations twice daily (n = 148), or an equivalent dose of budesonide 100 microg, two inhalations twice daily (n = 138). Efficacy variables included morning and evening peak expiratory flow (PEF), spirometery, asthma symptoms, and use of rescue medication (beta(2)-agonists). Serial FEV(1) assessments were carried out on a subgroup of children (budesonide/formoterol, n = 41; budesonide, n = 40) at randomization and at week 12. Relative to baseline, morning PEF (primary variable) increased to a significantly greater extent with budesonide/formoterol than with budesonide alone (7.22% predicted normal vs 3.45% predicted normal; P < 0.001). Evening PEF also increased significantly with budesonide/formoterol (6.13% predicted normal vs. 2.73% predicted normal; P < 0.001), as did mean FEV(1) and serial FEV(1) measured over 12 hr (both P < 0.05). Similar improvements in asthma symptoms and rescue medication use were observed in both groups. The two treatment groups were similar in terms of their adverse-event profile and rates of discontinuation. Budesonide/formoterol in a single inhaler provided rapid improvements in PEF and FEV(1) compared to inhaled budesonide alone. These improvements were sustained throughout the study period. Budesonide/formoterol was well-tolerated in children with moderate persistent asthma.

Administration, Inhalation↗
PubMed2001

[Unusual manifestations of Bartonella infections].

The authors review the cases of two patients with an atypical form of cat scratch disease. The first case exhibited ileocoecal and hepatoportal lymphadenitis, and the second case the emerging symptoms of a non-specific granulomatous process in the middle third of the right forearm, which caused a differential-diagnostic problem. Establishment of a diagnosis was possible only on the basis of the disease process and the pathological, serological and histopathological pictures of the lymphatic glands after other causes of the lymphadenopathy had been excluded. Following two weeks of antibiotic treatment, the patients were free of complaints- and symptoms. Bartonella antibody tests were performed on 5 cats living in the neighbourhood of the patients with titer determinations too in 3 cases.

Animals↗
PubMed2001

[Determination of the type and subtype of the hepatitis C virus in chronic viral hepatitis patients in Hungary].

The huge variability of hepatitis virus C is well-established. The geographical differences in its nucleotide sequence have important clinical significance by causing variant pathogenicities and affecting sensitivity to therapy. The authors pioneered the determination of the viral type and subtype in patients suffering from chronic viral hepatitis in Hungary. In this present work they report the applied methods and the results. In their virus serological laboratory was introduced the test "HCV Serotyping 1-6 Assay", which is based on the analysis of antibodies, in 1996. By this method they examined the samples of 127 patients and they found type 1 in 75.5%, type 4 in 25%, mixed types (type 1 + 2, 3, 4, 5, 6) in 9% and non-classifiable, non-reacting antibodies in 13% of the cases. Since 1999 they have used the combination of direct reverse-PCR of the viral antigen and reverse hybridization to type-specific specimens. These results, from 211 patients show that 6% belong to 1a, 85.5% to 1b, 3% to 1a + 1b, 1% to 1b + 2, 0.5% to 3 and 4% to mixed subtypes. Genotype 1b was associated with higher viremia. On the basis of the above they can conclude that 90% of the Hungarian population are infected by the most resistant 1b subtype of hepatitis virus C. It could explain the fact that only 20% of their patients with interferon monotherapy have become permanently virus-free. In view of these results they recommend combined, higher dose, long-lasting treatment in therapeutic protocols.

Adult↗
PubMed2001

Regulation of the expression of endopolygalacturonase gene PGU1 in Saccharomyces.

Previous work in our laboratory has shown that Saccharomyces bayanus strain SCPP is the only reported yeast expressing the three types of pectolytic enzymes: pectin esterases, pectin lyases and polygalacturonases. One of these enzymes, the endopolygalacturonase (endoPG), hydrolyses plant-specific polysaccharide pectin. The endoPG encoding gene (PGU1) is also present in Saccharomyces cerevisiae. It has been shown that this endoPG is required for the development of pseudohyphae. Using genomic DNA, the PGU1-1 and PGU1-2 promoters of these strains have been amplified and used to construct gene fusions with the beta-galactosidase gene. On the basis of beta-galactosidase measurements, we compared the expression of both promoters in different environmental conditions in order to identify their modulation. We have shown that the PGU1 gene is upregulated by the presence of the pectin and the product resulting from endopolygalacturonase activity. Moreover, expression of the PGU1 is also enhanced under respiratory and filament formation conditions.

Base Sequence↗
PubMed2001

Sonoluminescence and phase diagrams of single bubbles at low dissolved air concentrations.

We studied experimentally the dependence of light emission and phase space boundaries of air bubbles in water on the level of degassing down to low partial pressures of 15 mmHg. We found that the maximum obtainable light intensity increased monotonically by lowering the concentration of dissolved air in water. We also present a new technique to obtain the acoustic pressure (P(a)) and ambient radius (R0) parameters, based on the information provided by the timing of the flashes in the acoustic cycle. Using this technique we give phase diagrams of the bubble in the (R0,P(a)) and (P(a), gas concentration) space, and discuss the parametric dependence of the light intensity. The resulting power-law dependence of the relative intensity normalized by the ambient volume of the bubble on the expansion ratio indicates that more extreme conditions are attainable inside a bubble at dissolved air concentration of 15 mmHg than at 150 mmHg.

Journal Article↗
PubMed2001

A randomized trial of relapse prevention of depression in primary care.

BACKGROUND: Despite high rates of relapse and recurrence, few primary care patients with recurrent or chronic depression are receiving continuation and maintenance-phase treatment. We hypothesized that a relapse prevention intervention would improve adherence to antidepressant medication and improve depression outcomes in high-risk patients compared with usual primary care. METHODS: Three hundred eighty-six patients with recurrent major depression or dysthymia who had largely recovered after 8 weeks of antidepressant treatment by their primary care physicians were randomized to a relapse prevention program (n = 194) or usual primary care (n = 192). Patients in the intervention group received 2 primary care visits with a depression specialist and 3 telephone visits over a 1-year period aimed at enhancing adherence to antidepressant medication, recognition of prodromal symptoms, monitoring of symptoms, and development of a written relapse prevention plan. Follow-up assessments were completed at 3, 6, 9, and 12 months by a telephone survey team blinded to randomization status. RESULTS: Those in the intervention group had significantly greater adherence to adequate dosage of antidepressant medication for 90 days or more within the first and second 6-month periods and were significantly more likely to refill medication prescriptions during the 12-month follow-up compared with usual care controls. Intervention patients had significantly fewer depressive symptoms, but not fewer episodes of relapse/recurrence over the 12-month follow-up period. CONCLUSIONS: A relapse prevention program targeted to primary care patients with a high risk of relapse/recurrence who had largely recovered after antidepressant treatment significantly improved antidepressant adherence and depressive symptom outcomes.

Adolescent↗